In recent years considerable resources have been dedicated to the development of passive-type vehicle occupant restraint belt systems, that is, the type of occupant restraint system that operates by automatically moving a restraint belt to an occupant restraining position when the vehicle door is closed and automatically moving the belt to a release configuration when the door is opened. Many passive restraint belt systems have a belt transfer member, either a belt transfer ring or a movable belt anchor, that is driven back and forth by a drive device, such as a gear reduced electric motor or a mechanical motion amplifier, along a guide rail. The back and forth motion of the belt transfer member is transmitted to the transfer member from the drive device by a drive element, such as a racked wire, driven by an output gear of the drive device.
In most passive belt systems proposed heretofore, the drive wire has been fastened to the belt transfer member by a coupling device that is more or less permanent and is pre-installed by the manufacturer of the belt system. Indeed, the guide elements of the system, which include the guide rail, the belt transfer member and, in the case of a moving anchor, the locking device for the moving anchor, and the drive elements, which include the drive device and the drive element, constitute a single assembly. This single assembly is then installed in the vehicle during manufacture of the vehicle. The fact that the guide and drive parts of the passive belt system are made as a single assembly makes it more difficult to install the system in the production line of a modern vehicle assembly plant, and also makes it more difficult to disassemble the system for repair or replacement, should that be necessary.
It is apparent, then, that it is desirable that the passive system be manufactured as two sub-assemblies or groups, a belt guide group and a drive group. There then arises the problem of how to connect the two groups quickly and easily. One possibility is to provide an opening in the guide rail at a location near the restraint position of the belt transfer member for access to a suitable coupling that can be made between the belt transfer member and the drive wire after the guide group and drive group have been installed. While this solution is workable, it can slow down the assembly procedure because it is difficult to work within a very small opening in the guide rail. Moreover, the types of couplings suggested in the past involve rigid attachment of the drive wire to the belt transfer member, and the way in which the final assembly is accomplished leaves open the possibility that the drive wire may be twisted when it is done up and thereby impart a twisting force on the transfer member and a torsion stress in the wire. Rotational force imparted to the transfer member may effect the smooth running of the transfer member along the guide rail, and the torsion stress in the wire is undesirable.